Hydraulic weighing scale



Jan. l2, 1960 w. M. wlsE 2,920,654

HYDRAULIC WEIGHING SCALE Filed April 13, 1956 r/v//f EN. /mw A i /05464;(525' 4. 25 go Il I I P 53" 2@ j? 54 25 .En BY Ulllited Seres,llaffnf 2,920,654 HYDRAULIC WEIGHnvG SCALEV WilliamM. Wise, Royal Oak,Mich. Application April 13, 1956, serial No. 578,069

' p 1 4 claims. (ci. y137-778) This invention Arelates to hydraulicweighing scales, and particularly to improvements in the construction ofweighing scales of the general classdisclosed in my Patent No.2,643,873, issued June 30, 1953.

Y An important Vobject of the present invention is to provide animproved scale of the indicated variety, utilizing load sensing meanscomprising a' cylinder, a piston, and an interposed liquid adapted to bepressurized by the load, the `scale being so designed and constructedthat frictionV within theload sensing means. is reduced to an absoluteminimum.

11A further object is to provide such a scale which is highly resistantto variation of its characteristics due to. wear of parts, and theaccuracy of which is not disturbed by the imposition of lateral forces.

A further object'is to provide such a scale which is relatively simpleand. inexpensive to construct and to assemble, `as well as to charge andadjust.

Another object is to provide such a weighing `scale which is capable ofhandling very heavy loads `and which is itself of minimum weight.

Other objects and'advantages of the invention will become apparent-uponyconsideration of the present disclosure in its entirety. 'i v In thedrawing: Y Figure 1 is a side elevational view of a weighing scaleincorporating thepresent invention; and

' Figure 2 is a view on a larger scale, principally in longitudinaldiametriccross section, but partly in elevation, of the load sensingportionsy of thescale.

Referring now to the drawing, Ywherein my invention is illustrated in acrane scale mechanism, referencecharacter designates generally a steelcylinder within which a piston assembly generally designated 12 ismovably mounted, in such manner as to pressurize, in proportion to theload of the scale, a 4quantitytof a suitable liquid such as oil- (notshown) which fills the cylinder space 14 and which also fillscommunicating passages which are not fully shown but which include theconnecting tube 18, and a pressure responsive portion which will bereferred to hereinafter.

The piston assembly 12 is rigidly connected to a suspension eyegenerally designated 15 which is adapted to be suspended from a cranehook or other suitable support, and thel cylinder is rigidly heldagainst axial movement with respect to a hook assembly generallydesignated 16, from which a load to be weighed is adapted-to besuspended. 'The suspensionv eye 15 and hook 16 may of 18 tosuitableloadrindicating means (not shown) which may compriseaBourdontube-type or other appropriate pressure' gaugehousedwithinacasing portion 20 rigidly attached .as by ange ands'crew portions 22,24 to the side ofr the .vcylinden 10,v the ,casing 20 in turn supporting-a housing. portion -25 fora dial andpointer, byY which y 2 anindication of weight may be given. Such features are shown in my patentabove referred to and are known inthe art. n

As itsupper endthe cylinder is partially closed by a head ring 26 havinga concentric cylindrical internal wall 281 lThe cylinder is provided atits upper extremity with an inwardly projecting concentric flangeportion 30 which is of lesser axial length than and overhangs a part ofthe head ring 26. The lower portion of the head ring has -a lflangeportion 32 which projects outwardly to underliezthe inwardly directedcylinder flange 30. The head ringt'26 isv inserted from the lower end ofthe cylinder yand is locked against upward displacement by the graduateddiameters of such overengaging flange portions -30, 32.. The head ringis alsofsecured in place by -radial'lock screws as 33. A perfect sealybetween the cylinder andhead lring is insured by an O-ring 34 fitted ina suitableperiph'eral groove in the head ring and compressed between thehead ring and cylinder wall.

The piston 12 has a reduced upper extremity or neck 35 which has an easysliding fit in the bore 28 in the heardV ringl 26 and which is provided.with a peripheral 4groove 36 in which an O-type sealing ring 38 isfitted,

which maintainssealing engagement with the surface 28 of 'the' headring. At its upper extremity the reduced piston portion 35 is providedwith a peripheral rabbet 40 havinga lat bottom surface 42 and in which aherdenedI steelwear ring 44 is tted and held fast with respect to `thepiston. .fThe ring 44 is provided with a smaller peripherahrabbet 45. atits lower end which coacts withathe flat surface42 to deline aperipheral groove within which aplurality of bearing balls 46 areaccommodated. ,The ring 44 and the inner surface of head ring 46 arehardened, so that they will not be worn substantially by the hardenedsteel balls 46, but the main -body portion of the piston 12 need not behardened.

The central portion 69 of the piston is-y accurately nishedto haveV avery slight clearance with respect to the internal wall 77 of thecylinder and is sealed with respect thereto by an 0-ring 73 carried bythe piston.

The `straight cylindrical stem portion 48 of the suspension eye 15 isheld against upward displacement with respect to vthe piston by a lockring assembly 50 formed in two `semi-circular halves and projectingradially inwardly into a peripheral groove 52 in the shank 48 and alsoprojecting radiallyoutwardly from the shank to partially underlie theupper wall 53 of a counterbored portion 54 formed concentrically in thelower extremity of the'y piston 12. The diameter of the downwardlylopeningfcounterbored portion 54 substantially exceedstheoutsidepdiameter of the ring assemly 50, and a filler ring.5 5 isfitted in the counterbore around the ringassemlbly 50 toprevent outwarddisplacement of the two sections `of the latter. The retaining ring 50is heldin place by an internal snap ring 56` fitted in an internal slot(undesighated) Ain the counterbored portion 54, below the retain- .ingringv The shank 48 of the suspension eye projects downwardly below thepiston and forms a lower bearing-supporting portion, being extendedthrough a cylindrical opening 58 in a bearing wall 60 which extendsacross the `cylinder spacedly beneath the piston and which is pressed orotherwise rigidly secured in place. The bearing wall 60 mayV also beformed of steel, and its cylindrical internal bearing surface, which isconcentric with the cylinder,

is hardened. A bearing ring 62is secured to the lower end ofthe shank ina position opposite the bearing Wall 58, andl is provided with aperipheral groove 64 in which a series of hardened steel bearing balls65 are tted. The ring 62, or at least the outer face portion having theball groove therein, is also hardened.

Theskirt of the piston 12 is cut away in an area, des- `acarrear belowthe piston head portion 70 to the lower end of the piston.. The upperend: of the cutaway portion 68 preferablydefines a truncatedeon'ic' wall71`which`, at its lower end, joins a vertical-cylindrical `wall 72spaced outwardly from vand surrounding the counterbored; lpoi",- tion5.4. The inclination of the wall `71 may besuch as to reinforce'the head7l) against which the principal pres'- sure resulting from loading ofthe scale is exerted.

. All ofthe parts except the shank 48 are fitted into the cylindern fromthel lower end, the cylinder being counterbored in a plurality of stepsof successively graduatedly `load of200,000J lbs. Therpowerr required todistort the rO-rings is accordingly very l`low. In addition, it isunidecreasing diameter upwardly from the lower end. Such fcounterborings of the cylinder are performed in such manner 'as toprovide a'shoulder 66 to limit upward movemerit of thebear'ing wall 60and accurately locate the latter.

The lower end of the cylinder is closed by a head gen.- erally/designated 75 which may, as shown, be providedat its lower end with anexternally threaded portion 76 screwed into. a conformably internallythreaded portion V77 at the lowerend of the cylinder, and suitablylocked in place, as byrlock screw means. 78. The lower head 75 extendsupwardly within the' cylinder yand is provided with a relatively deepaxial counterbore 80 at its upper end communicating with an .axial bore82 extending' vdownwardly and completely through the head.

The shank 84v of the hook 16 extends upwardly throng the bore 82 andcounterbore 80 and isl provided within the area surrounded by thecounterborey with a peripheral groove y85. A lock ring 86 is tted .intoand' projects radially outwardly from the groove 85' and may be formedform at each actuation of the scale, and does not introduce staticfriction. The reduced upper neck 35 and ring 44, fitted within the tophead ring 26 are valso freely slidable in the bore 28, and the ring 62has a free sliding fit in the bearing ring v60. The neck 35 and thedownwardly projecting portion 48" of stem 48 are accurately centered bythe bearing balls 46j and' 65 respectively, so that these portions, actas pilots for the piston, and it will be appreciated' that friction isheld to an absolute minimum by the reduction in diameter of such pilotparts which are mounted in the ball bearings. By reason of the widevertical spacing of the two' bearings dened by the balls 46-65, anynonaxial loads tending to tilt the piston with respect to the cylinderapply minimum radial loads to the balls and races, so that they cannotbe dis- `tortedrenough to introduce appreciable statirc'frictionl AOnlythe surfaces. .which are directlyengaged by the balls 'need behard'enedand such'surfaces are carried byy parts travelfis very slight, asindicated above, it is advantageous to minimize any variation ofpressure below thepisfion. yinasmuch as scales. of this typel may beleft out ondoors in all; kindslfof weather, it is also advantageous toformthe lowerhead 75 as a closure; as shown, even in two semicircularsections, as'in the' case of thelrin'g t 50, andrsimilarly held againstescape fromthe groove rby a retaining ring 88 which fills the radialspace be.-

tween the ring 86 and the internal-wall of the counterbore 80 andvblocks escape of the sections ofthe ring-86.

Upward escape of the filler ring 88 is prevented by aniriignated' 95 andthese roll upon a bottom race plate 96 seated on the bottom of thecounterbore. It will be ap-v preciated that if rotary force is applied4to the hook', 'it

and its shank84 may turn freely with respect to the scale body on thebearing rollers 95.

As. previously noted, all of the components contained within thecylinder 10 are assembled from thelower end,

- with the exception of the shank 48 of vthe suspension eye.

It will be apparent that after the piston 12 is inserted,

the shank 48 is pushed in from above and then-locked.Y from theunderside of the piston by the insertion of" the `lock ring sections 50and retaining ring'55 and snap' ring 56. The bearing ring 62 is alsoinserted over and secured to the lower end of the shank from beneath.This ispreferably done after t-he bearing plate 160 isv inserted, sincewthis facilitates the insertion ofthe-bearing balls 65. The

bearing plate 60 is preferably locked against downward displacement by aplurality of abut-ments 98 (only'one of which is shown in the drawing)extending upwardly fromy the top of bottom head 75. These may, as shown,Y comprise machine screws fitted inv suitably positioned tapped holes inthe head and heldin preliminarilyV adljusted positioning asby a lockAnut 100.

Any important consideration in achieving accuracy` and assembly.The-rollers of the bearing assembly are des- 'Y ameters of saidwallportions decreasing progressively though theA pressure uid is,entirely above the piston, in orderfto keep vout atmospheric. moistureand'V minimize oxidation? The apertures 61. allow'the space belowbearing support plate., 60 to act asi a part of the air chamber belowttl'ie piston, thereby-reducing the lcompression ratio and, thus, -therange ofrpressure variance and the resistance to piston movementdeveloped below the piston. A limp annular weather seal' member as V105may also be providedatthe top, bridging, and ysecured lat its innerandouter peripheries to, pilot neck 35 and head ring 26, respectively. yv Y 'While it wil-l1 be apparent thaty the preferred'` embodiment of theinvention herein described is well calculated to fulfill the objects andadvantages firstV above-stated, it

will be appreciated that the invention isfsusceptiblev to variation,modification and change without` departing `Iclaim:, Y f.

1;. In a hydraulic weighing scale construction, a hollow "cylinderincluding a plurality of internal cylindrical wall portions ofdifferent diameters andhaving. a head closure member atg one endprovided with an axially positioned aperture defining-y a, hardenedinternal surface, said difrom said end of the cylinder toward the otherend, a

`piston fitted in said cylinder and having a skirt portion operativelyintertted with afwall portion of said cylinder of intermediate diameter,an annular bearing member :fitttedinto saidv cylinder onl the oppositeside of said skirt portion fromsaid closure memberv and held` inaportion Aof said cylinder which. is larger than the cylinder portionjwithwhich the lskirt portion is intertted and which is v spaced fromsaid pistonY in an axial direction, saidY annular bearingI memberhavingA a' hardened and apertured internal bearing portion deiiningtanlaperture-y extending sensitivityin a hydraulic scale is-,thereduction ofV fricn `tion to an absolute minimum. The use of a piston,rather than a diaphragm, is desirable from the standpoint of accuracyand linearity. `In the present construction the largest' portion 69 ofthe pistonl is so fitted as to move freely but 'accurately withinthecylinder. It will be appreciated that the actual' travel` is veryslight, being ofthe vorder of a f'ew'thousandthsofY auf inchinaxiinuni-V for a ltherethrouglr coaxially with respectf to the piston,a re- 'ducedf bearing supporting portion concentricallyriixed. to -thepiston and extending upwardlyfrom said skirt portion into interttedrelation with, but ofsubstantially smaller Idiameter than, tliefirst-mentioned'v aperture-dening. surrfacer a liarden'edlring on saidbearing-supporting portion, i' antifrictionk bearingqmean's-reactin'gagainst said. ring and vaga'ins'rsaitl hardened surface'of the. headvclosuremem-l ber, a second reduced bearing supporting portionconcentrically xed to said piston and projecting downwardly from saidskirt portion into interfitted relation with, but being of substantiallysmaller diameter than said aperture in the annular bearing member, ahardened ring on said second bearing-supporting portion, andantifriction bearing means coacting with said last-mentioned ring andwith the aperture in the annular bearing member.

2. Means as deiined in claim 1 wherein said head closure member is ofgraduated external diameter and has its portion of larger diameterfacing said skirt portion of the piston and is interlitted with asimilarly graduated internal surface of the cylinder, being therebylocked against movement away from the skirt portion.

3. Means as defined in claim 1 wherein said head closure member is ofgraduated external diameter and has its portion of larger diameterfacing said skirt portion of the piston and is interlitted with asimilarly graduated internal surface' of the cylinder, being therebylocked against movement away from the skirt portion, said skirt portionbeing spaced from said head closure member to define a pressure space,an O-ring-type seal carried by said first-mentioned reducedbearing-supporting portion and sealing the same with respect to saidhead closure member, and a second O-ring-type seal carried by said skirtportion and sealing the same with respect to the cylinder.

4. In a hydraulic scale or the like, a hollow metallic cylinder having ahead at one end, a piston reciprocable in the cylinder, a pilot neckextending rigidly from and forming a fluid-tight extension of the pistonon one side of the latter and extending slidably through an aperture insaid head, bearing and sealing portions for guiding and sealing thepilot neck with respect to the head, tensioning means also connected tothe piston for urging the piston toward said head to pressurize a liquidtrapped between the piston and head, said tensioning means extendingoutwardly from the piston in the same direction as said neck and beingaccessible from outside said head, a transverse bearing support rigidwith respect to said cylinder on the opposite side of said piston fromsaid head, a pilot portion extending rigidly from the other side of saidpiston to travel therewith and slidable in an aperture in said bearingsupport, coacting bearing portions carried by said pilot portion andbearing support, said neck and pilot portion being of substantiallysmaller diameter than the piston, and said bearing portions holding thepiston against axial misalignment with respect to the cylinder, saidbearing portions including opposed hard metallic sections carried bysaid neck and head, and bearing balls interposed between and reactingagainst said opposed sections, opposed hard metallic sections carried bysaid pilot portion and support, bearing balls interposed between andreacting against said last-mentioned sections, and second tensioningmeans secured to said cylinder and extending in the opposite directionfrom said first-mentioned tensioning means.

References Cited in the ile of this patent UNITED STATES PATENTS1,798,076 Frisch Mar. 24, 1931 1,822,628 Lincoln Sept. 8, 1931 2,532,663Ellis Dec. 5, 1950 2,643,873 Wise June 30, 1953

